Field of the Invention
The present invention relates to a method for generating forward error correction packets in a multimedia system and a method and apparatus for transmitting and receiving forward error correction packets.
Description of the Related Art
Due to increasing types of content and increases in the number of high-volume or high-data content such as High Definition (HD) content and Ultra High Definition (UHD) content, data congestion is increasingly worse in communication networks.
FIG. 1 schematically shows general Internet Protocol (IP)-based network topology and data flow.
Referring to FIG. 1, due to the data congestion, content sent by a sender 110, which may be a host A, may not be fully delivered to a receiver 130, which may be host B, and some of the content may be lost in its route from the sender 110 to the receiver 130. In a typical IP network, data is transmitted on a packet basis, and thus, it may be lost on a transmission packet basis. Accordingly, the receiver 130 may not receive the transmission packet lost in the network, and thus may not find out data in the lost transmission packet, causing a variety of user inconveniences, including audio quality degradation, video quality degradation, screen cracks, missing subtitle information, and file loss.
Therefore, there is a need for a method for repairing or recovering data lost in the network. Accordingly, the sender 110 may generate Forward Error Correction (FEC) frames by FEC-encoding source data and adding repair data thereto, and may transmit the FEC frames through a series of processes. In an application layer of a protocol stack, unlike in a physical layer where transmission data is received in the transmission order, transmission data may not be received in the transmission order in the application layer as it passes through a plurality of routers 150 in the network. Thus, there is a need for an ordering method for allowing a receiver to determine the order of each of symbols in FEC frames and a packet generation and transmission method for allowing the receiver to get boundary information between FEC frames.
An IP packet 170, as shown in FIG. 1, may be transported to the receiver 130, passing through the plurality of routers 150. However, the IP packet 170 may be transported to the receiver 130 in a different order than the order that the sender 110 transmitted the packet 170. Accordingly, there is a need to indicate a transmission order of packets in Audio/Video (AV) content streaming. To this end, it is preferable that, in an application stage, data 171 in FIG. 1 may be regarded as RTP packet data that is generated by packetizing data compressed in an AV codec stage, using a Real Time Protocol (RTP), or may be regarded as Motion Picture Experts Group (MPEG) Media Transport (MMT) packet data.